Location

It is a fortified pass allowing access from Udûn. The only way through is over the bridge which spans a flaming ditch on each side of the wall and passes through the gates, which have been wrenched asunder following Sauron's fall.

Quests

Creatures

Lore

The Isenmouthe (Archaic Westron) or Carach Angren (Sindarin) (both meaning Iron-mouth) is the pass between the small valley, Udûn, and the larger expanse of the Plateau of Gorgoroth. It is formed where spurs of the ranges of the Ephel Dúath and Ered Lithui met, leaving only a narrow passage between them.

Representing the passage to the Black Gate of the Morannon, Carach Angren was heavily fortified, and both the rocky spurs that overlooked it carried fortresses and watchtowers. Across the passage itself, a wall of earth had been built, and a great ditch had been dug across the opening spanned by a single bridge.[1]

When Sauron was defeated, the blast of heat from the eruption of Orodruin severely damaged the gates. The servants of Ugrukhôr were unable to close them, but made an attempt to prevent anyone from passing.[2]

↑J.R.R. Tolkien, The Lord of the Rings, The Return of the King, "Mount Doom"